Alumina Ball Research Articles

Effect of carbon nanotubes on the biotribological behavior of hot-pressed PEEK-based composites for biomedical applications

This study aims to evaluate the influence of carbon nanotubes (CNTs) content (0.1, 0.5, 1, and, 5 wt%) on the poly-ether-ether-ketone (PEEK) composites based on a veneering concept and produced by the hot-pressing technique. Biotribological tests were performed in a ball-on-plate geometry using an alumina ball as the counter body under a phosphate-buffered saline solution at 37 °C, assessing the coefficient of friction and specific wear rate. Hardness measurement, white-light interferometry, and scanning electron microscopy were employed to support the study. The results revealed that the carbon nanotubes exhibited a positive influence on the biotribological behavior resulting in 1 wt% CNT proved to be the optimized value. Such findings could engineer high-performance surfaces as load-bearing materials in biomedical applications.

Storage and heat dissipation behavior of a heat storage ball with an Al–xSi alloy core and alumina ceramic shell

Regenerative thermal storage systems are becoming increasingly popular for recycling large amounts of waste heat generated in industrial furnaces every year. In order to improve the efficiency of regenerative burners, encapsulated phase change material consisting of an Al–Si alloy core sealed in a spherical ceramic shell has been proposed as a promising heat storage material. This is due to its melting temperature of 850 K, high heat storage density, and high heat storage rate under high-temperature operating conditions (over 773 K) with a short burner switch time. This study conducted rapidly heat storage simulation based on finite element method, heating and cooling tests and microstructural analysis to compare the properties of conventional solid alumina heat storage balls with those of the proposed core–shell heat storage ball with different Si concentrations. It was confirmed that the core–shell ball can store latent heat and is superior to the conventional solid alumina ball in terms of heat storage rate and heat storage density. The eutectic composition of Al–12.2% Si was determined as the optimal core composition for rapid high-temperature heat storage owing to its high heat phase change rate and density over a short time.

Dissolution mechanism of alumina inclusions into CaO–SiO 2 –Al 2 O 3 –Fe t O–MgO slag via a converter tapping process

Reducing the amount of inclusions during the steelmaking process as much as possible and much earlier plays a vital role in improving the quality of steel products. To reveal the dissolution mechanism of inclusions in slag during the converter tapping process, some comparison experiments were conducted by adding isolated spherical alumina balls as inclusions in CaO–SiO2–Al2O3–FetO–MgO slag, and FetO content up to 10% was contained in slag. The results showed that the dissolution rate of alumina balls in the slag was mainly affected by the diffusion of Al2O3, and the diffusion coefficients of Al2O3 were 4.2 × 10–11, 7.5 × 10–11, and 1.5 × 10–10 m2/s at 1500℃, 1550℃, and 1600℃, respectively. In addition, the upgraded diffusion-distance-controlled dissolution model (DDD-Model), in which FetO content was introduced and applied in the study. The results illustrated that the Al2O3 inclusion apparent dissolution rate was improved by a high FetO content, increasing CaO/SiO2 and raising the temperature as soon as possible at the early stage of the converter tapping process. It is not necessary to increase the FetO content in the slag to enhance the dissolution rate of the Al2O3 inclusion at the last tapping stage. The predicted complete dissolution time of spherical Al2O3 inclusions with 1000 µm in diameter based on the upgraded DDD-Model was approximately 1796 s during the actual converter tapping process.

Sliding wear behavior of a sustainable Fe-based coating and its damage mechanisms

The current industry demand is to identify suitable alternatives to the risk-of-supply prone and/or toxic, WC-Co and electrolytic hard chrome coatings without comprising the desired wear performance. Therefore, compositions based on abundantly available elements (e.g. ‘Fe’) that possess adequate wear resistance are desirable from health, sustainability and economic standpoints. In this work, crystalline Fe-based (Rockit-401) coatings were processed using two different thermal spray routes, i.e. HVOF and HVAF spraying. The influence of deposition route and processing conditions on the microstructure, porosity content, hardness and phase composition was examined. The as-deposited coatings were subjected to mild (5 N) and harsh (15 N) dry sliding wear test conditions by employing alumina ball as the counter surface material, and their wear performance was examined. Mild sliding wear test conditions (5 N) resulted in anomalous wear behavior, where the abrupt drop in CoF at several instances during the test was observed in all the investigated coatings. On the other hand, under harsh wear test conditions (15 N), such an abrupt dip in CoF was not observed. Detailed wear mechanisms of the coatings were revealed under different test conditions (5 N and 15 N). This work sheds light on processing, wear behavior and wear mechanisms of a sustainable and high-performance coating that fulfills non-toxic and sustainability goals in tandem for tribological applications.

Dry and grease-lubricated reciprocating wear resistance of borided AISI 52100 steel

This work presents new results about the dry and grease-lubricated wear resistance of borided AISI 52100 steel. Boriding was conducted at 850 °C for 1 h. The reciprocating wear tests were conducted with an alumina ball of 6 mm of diameter, with normal load of 20 N and sliding distances of 100, 150 and 200 m; a lithium grease was employed for lubrication. In comparison with heat-treated AISI 52100 steel, boriding reduced the coefficient of friction by 15–30% in dry conditions, although both stabilized similarly in grease-lubricated tests. In addition, the results showed that, for the longer sliding distance, boriding increased the wear resistance up to 8 times in dry conditions and up to 10 times using grease for lubrication. The implementation of boriding significantly improved the tribological performance of AISI 52100 steel in both tests conditions.

Role of B2O3 and CaO in Al2O3 matrix composite: In-situ phases, density, hardness and wear resistance

A novel set of Al2O3-B2O3-CaO composites were manufactured using a cold press-sintering. The B2O3 content in the composites was varied from 5 to 20 wt% and 2 wt% CaO was added to the composites. Dry sliding tests were conducted against an alumina ball at 10–95% relative humidity. The presence of the in-situ formed aluminum borate in the composite enhanced the micro-hardness and wear resistance, whereas the humidity-sensitive alumina phase reduced friction. Furthermore, addition of CaO improved the relative density upto ~92% which also led to significant improvement in hardness and wear resistance. However, the friction was negatively affected. The mechanism for enhanced wear resistance is demonstrated by considering the crystal-chemical approach and polarization theory for the double oxide systems.

Thermal oxidation of a porous Ti[sbnd]23Nb alloy for wear related biomedical applications: Effect of oxidation duration

In this study, an attempt has been made for tailoring the surface features of an 18 vol% porosity containing Ti23Nb alloy manufactured via powder metallurgy method. The aim was enhancing the wear resistance without sacrificing the mechanical properties. For this purpose, porous Ti23Nb alloys having hardness of 280 HV0.025 were subjected to thermal oxidation (TO) at 600 °C in air for two different holding times. TO duration of 6 h, which introduced a ~ 0.5 μm thick TiO2-rutile type exterior oxide layer (OL), provided surface hardness of 620 HV0.025. Extension of TO duration to 60 h caused covering of the surfaces with a ~ 3.0 μm thick OL and increase of surface hardness to 980 HV0.025. As the result of the increased surface hardness, TO'ed. alloys showed superior sliding wear resistance coupled with a reduction in friction coefficient (COF) against alumina ball in 1.5× simulated body fluid (SBF) when compared to the as-sintered state. Despite having the highest surface hardness, the alloy TO'ed. for 60 h exhibited slightly higher wear loss and COF than the alloy TO'ed. for 6 h. More important than this, the alloy TO'ed. for 60 h collapsed at a compressive stress well below the yield strength of the alloy TO'ed. for 6 h, which exhibited almost similar compressive stress-strain curve with that of the as-sintered alloy. From this perspective 6 h appeared as a promising TO duration for the examined porous alloy to be used in biomedical applications as it preserves the mechanical properties while providing remarkable enhancement in the wear resistance.

DRY SLIDING FRICTION AND WEAR OF THE WC/TIC-CO IN CONTACT WITH AL2O3 FOR TWO SLIDING SPEEDS

The paper examines the friction and wear behavior of four different WC/TiC-Co cermets, where three of them are composed of 5%, 10% and 15% TiC additions, and a WC-Co grade without TiC, taken as a reference material for comparison purpose. The principal aim is to improve wear resistance to high sliding speeds (hot rolling) of the WC-Co material as a reference by adding previously-listed percentage of TiC. The samples (cermets) were prepared according to the powder metallurgy procedure, which includes the preparation of the powder mixture, its compression shaping and liquid phase sintering. Sintering was carried out at 1460 ° C, for 14 hours, in a reducing medium (H2). The TiC materials are added in order to boost hardness of the WC-15Co cermet and, consequently, its resistance to wear under thermomechanical conditions. The experiments are conducted using a pin-on-disc tribometer in contact with Al2O3 alumina ball at two sliding speeds of 0.5m/s and 0.75m/s, at a high temperature of 450°C, and a 20 N load. It has been noticed that some recorded friction coefficients are unstable and exhibit many peaks during almost the whole friction test period. The obtained results from the SEM microscope show that the wear behavior of the new proposed material is improved, where it has been shown that, at the sliding speed of 0.75m/s, the greater the TiC percentage is, the lower the average friction coefficient will be. Also, for the speed of 0.5 m/s, the average friction coefficient is relatively more stable with the TiC percentage increase. Moreover, the obtained experimental results show an average wear rate decrease, with respect to reference grades (NA), that amounts to nearly 36% and 41% at the two sliding speeds P1 (0.5m/s) and P2 (0.75m/s), respectively.

Effect of Steel Hardness and Composition on the Boundary Lubricating Behavior of Low-Viscosity PAO Formulated with Dodecanoic Acid and Ionic Liquid Additives.

Two ionic liquids, tributylmethylphosphonium dimethylphosphate (PP) and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMP), as lubricant additives in polyalphaolefin (PAO8) were studied under boundary lubricating conditions on two types of steel (AISI 52100 bearing steel and AISI 316L stainless steel). The tribological behavior of these ILs was compared with dodecanoic acid, a well-known organic friction modifier. This study employs a ball-on-disk tribometer with an alumina ball as a counterpart. A range of advanced analytical tools are used to analyze the tribofilms, including scanning electron microscopy equipped with a focused ion beam, scanning transmission electron microscopy equipped with X-ray energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. A quartz crystal microbalance with dissipation was used to study the surface adsorption of the additives on iron- and stainless steel-coated sensors to reveal the adsorption kinetics, adsorbed layer mass, and bonding strength of the adsorbed layer on the metallic surfaces. The most important factors controlling friction and wear are the thickness and viscoelastic properties of the adsorbed layer, the thickness and chemical composition of the tribofilm, and the hardness and chemical composition of steel. Among all additives studied, BMP on stainless steel gives a strongly adsorbed layer and a durable tribofilm, resulting in low friction and excellent antiwear properties.

High-Temperature Wear Performance of hBN-Added Ni-W Composites Produced from Combustion-Synthesized Powders

This work reports on the spark plasma sintering (SPS) of self-propagating high-temperature-synthesis (SHS)-derived Ni-W and Ni-W-2wt%hBN (4:1 molar ratio of metals) powders. The synthesis was carried out from a mixture of NiO and WO3 using Mg + C combined reducers through a thermo-kinetic coupling approach. Experiments performed in the thermodynamically optimal area demonstrated the high sensitivity of combustion parameters and product phase composition to the amount of reducers and hBN powder. The powder precursors with and without the addition of hBN were consolidated using SPS at a temperature and pressure of 1300 °C and 50 MPa, respectively, followed by a thorough phase and microstructural characterization of the obtained specimens. SHS-derived powders comprised the nano-sized agglomerates and were characterized by a high sinterability. The specimens of >95% density were subjected to ball-on-plate dry sliding wear tests at a sliding speed of 0.1 ms−1 and a distance of 1000 m utilizing an alumina ball of 10 mm in diameter under a 15 N normal load. The tests were performed at a temperature of 800 °C. A significant improvement in wear behavior was demonstrated for SHS-processed composites in comparison with their counterparts produced via conventional high-energy ball milling technique owing to the phenomena of ‘micro-polishing’, cyclic ‘self-healing’ and fatigue. However, the decisive effect of hBN addition in imparting lubrication during an HT wear test was not confirmed.

Sliding wear and friction behaviour of WC‐stainless steel and WC–Co composites

AbstractThe sliding wear and friction behaviour of new developed WC‐stainless steel composites without and with carbon addition were evaluated using a linearly reciprocating sliding tribometer under ball‐on‐flat configuration, sliding against an alumina ball under unlubricated conditions. The wear of both, discs and ball were measured for different applied loads, sliding distances and frequencies. Worn surfaces were investigated by using microscopy and topography techniques. Comparative experiments were performed using flat samples of a conventional WC–Co composite. It was found that the WC–Co grade displayed an undoubtedly better sliding wear resistance and lower coefficient of friction if compared with the newly produced WC‐SS composites.

Control of textural property in spherical alumina ball for enhanced catalytic activity of Ni-supported Al2O3 catalyst in steam–methane reforming

Designing Ni-based catalyst with high performance is one of the most important challenges for operation of practical steam-methane reforming (SMR) processes. We report control of the textural properties of commercial alumina ball for Ni-supported catalysts in SMR. The textural properties of the commercial Al2O3 sphere are successfully controlled by aqueous HCl treatment for elongated periods. The pore diameters and pore volumes of the controlled alumina supports are finely tuned by varying the HCl treatment period. The catalytic activity of the corresponding Ni-supported alumina is significantly enhanced with increasing HCl treatment period on alumina ball. The alumina supports with longer HCl treatment period have larger pore size and bigger pore volume, and the corresponding Ni-Alumina catalysts exhibited higher catalytic activity at even higher space velocity, due to the increased intraparticle diffusion of reactant molecules inside the catalyst. Ni-supported alumina catalyst prepared by using alumina support treated with HCl for 18 h showed the largest pore size and pore volume, revealing enhanced catalytic activity in terms of CH4 conversion and H2 yield. It showed the well-maintained activity without any further deactivation in both continuous operation for 24 h and cyclic operation at different WHSV conditions.

Tribocorrosion performance of 316L stainless steel enhanced by laser clad 2-layer coating using Fe-based amorphous powder

To improve the tribocorrosion performance of 316L stainless steel (SS), multi-layer (1, 2 and 3 layers) Fe-based alloy coatings were manufactured by laser cladding Fe-based amorphous powder on 316L SS, and the corrosive wear behavior was investigated against Alumina ball in Ringer's solution. With the increase of cladding layer number, the content of body-centered cubic (BCC) phase increases, and the hardness also improved. The volume loss rate of SS at 5 N load decreased over 3 times by the 2-layer coating. Under 10 or 20 N loads, the 2-layer coating still presents the best tribocorrosion performance with the lowest values of friction coefficient and volume loss rate. The multi-layer cladding caused surface chemical composition change leading to the decrease of Cr accompanied with the increase of Mo and Y, which is responsible for the increase of BCC content and hardness as well as the formation of lubricant Fe–Cr hydroxide film. The friction induced lubricating film may facilitate to design new metallic coatings for the low carbon steels applied in corrosive environment.

Influence of Combined Mechanical Processes on Tribological Properties of Tool Steels Vanadis 8 and Vancron 40 With a Similar Hardness

Surface integrity is important factor for components exposed to wear, like cold working tools, which need to possess high hardness combined with high wear resistance. Surface treatments such as grinding, hard turning, and hard turning with slide burnishing have been developed for its improvement. Vancron 40 and Vanadis 8 tool steels, of different chemical composition and different types and amounts of carbides, were now investigated. Heat treatment was carried out in vacuum furnaces with gas quenching to hardness of Vancron 64 ± 1 HRC and of Vanadis 65 ± 1 HRC. 3D topography, optical and scanning electron microscopy, X-ray diffraction and ball-on-disc tribological tests against Al2O3 and 100Cr6 balls as counterparts were used to examine wear and friction. For both steels, the lowest values of dynamic frictions and wear rates against Al2O3 counterbodies were achieved after sequential process of hard turning with slide burnishing with a burnishing force of 180 N. For alumina balls, the increase of wear resistance, achieved after hard turning plus burnishing in comparison to grinding exceeds 50 and 60%, respectively for Vanadis 8 and Vancron 40 steels.

Influence on Tribological Behavior of PEEK Composite Film Layer on PEEK-PTFE Bearings with Artificial Defect in Dry Condition

In order to explore influence on tribological behavior of PEEK composite film layer in PEEK-PTFE composite radial alumina ball bearings, rolling contact fatigue tests were performed by using the PEEK bearing’s inner rings with the artificial defects in dry condition. When rotation speed and applied load were 600 rpm and 98 N, the number of cycles of the PEEK-PTFE bearings reached 1.0×107 fatigue cycles. The artificial defects with 0.02 mm depth on the raceway surface of the PEEK inner ring was covered with PEEK composite film accumulation.

Zeolite/Cerium Oxide Coat-on Activated Alumina Ball for Arsenite Removal via Fixed- Bed Continuous Flow Adsorption Column

Arsenite (As(III)) has threatened human life for ages. It is a necessity to remove As(III) from the contaminated water before general use. With the improvement of adsorption, higher As(III) removal can be achieved. This study aimed to develop zeolite/cerium oxide coat-on activated alumina ball adsorbent (CeZ-ball) with the aid of PVA binder and apply it to a fixed-bed continuous flow column for As(III) adsorption. The coating percentage of CeZ-ball was studied. Cerium ions leaching from CeZ-ball were monitored throughout the 2,880-min-column run to confirm the stability of CeZ attached to an activated alumina ball. Surface area, pH point of zero charge, and structural property of CeZ-ball were characterized. An average CeZ coating of 83.3% and rare leaching of cerium proved the coating method. The models proposed by Yoon-Nelson provided the most satisfactory fit with the breakthrough curve (r2 = 0.985, MPSD = 2.547, and q0 = 3.481 mg·g–1) under experimental conditions of the flow rate of 5 mL·min–1, As(III) influent concentration of 1 mg·L–1, and CeZ-ball weight of 40 g. The half-time of breakthrough (τ) was 1,228.739 min. The effects of the key parameters, including initial adsorbent weight, initial flow rate, and initial As(III) concentration, were investigated for the performance of As(III) adsorption. Simulated from the Yoon-Nelson model, the τ increased as well as the adsorbent weight but decreased as the flow rate increased, thus impacting the As(III) concentration. With the optimal condition, the fixed-bed continuous column with CeZ-ball could be used in As(III) removal from contaminated water.

Investigating load-dependent wear behavior and degradation mechanisms in Cr3C2–NiCr coatings deposited by HVAF and HVOF

Wear resistant coatings that comply with non-toxic environment goals are highly desirable. Cr3C2–NiCr is a promising alternative to the toxic, ‘Co’- containing WC–Co coatings to mitigate wear. The purpose of this study was to examine the suitability of Cr3C2–NiCr coatings for automotive brake disc application by systematically investigating their dry sliding wear behavior at different test conditions. Therefore, High Velocity Air Fuel (HVAF) and High Velocity Oxy Fuel (HVOF) were employed to deposit Cr3C2–NiCr coatings. The powder feedstock and as-deposited Cr3C2–NiCr coatings were characterized for their microstructure and phase composition using SEM and XRD. Mechanical properties (hardness, fracture toughness), porosity and surface topography of the as-deposited coatings were evaluated. The coatings were subjected to sliding wear tests at different normal loads (5 N, 10 N and 15 N) using alumina ball as the counter surface. Coefficient of friction (CoF) evolution of HVAF and HVOF deposited coatings, along with their wear performance, was obtained for different normal load conditions. The wear performance ranking of HVAF and HVOF processed coatings was influenced by the test conditions, with HVAF coatings demonstrating better wear resistance than HVOF coatings at harsh test conditions and the HVOF coatings performing better under mild wear test conditions. Detailed post-wear analysis of worn coatings, the alumina ball counter-body and the resulting debris was performed to reveal the degradation mechanisms at different test conditions. Findings from this work provide new insights into the desirable microstructural features to mitigate wear, which can be further exploited to deposit wear-resistant coatings.

Tribological behavior and self-repairing performance of chromium oxide films over multiple thermal cycles from 25 °C to 1000 °C

Chromium oxide film was prepared on the surface of Inconel 718 alloy by multi-arc ion plating; and the as-deposited film was annealed at elevated temperatures of 960 °C, 980 °C, and 1000 °C. The as-deposited and annealed films were characterized by scanning electron microscopy-energy dispersive spectrometry, high-resolution transmission electron microscopy, and X-ray diffraction. Their mechanical properties were determined with a nanomechanical testing system and a scratch tester, and their friction and wear behavior at ambient temperature and elevated temperatures of up to 1000 °C was evaluated in relation to the formation of the network-like surface bulge structure. It was found that high-temperature annealing treatment of the as-deposited chromium oxide film generates a unique surface bulge structure, which is due to the segregation and oxidation of the elements in the substrate alloy towards the grain boundaries thereat. The bulge structure transforms the plane contact mode of the annealed films sliding against alumina ball in a ball-on-disk configuration to a point contact mode, which is beneficial for reducing the friction coefficient and wear rate of the annealed films over multiple thermal cycles. Moreover, the bulge structure damaged during sliding can be regenerated and replenished by secondary annealing, which provides the chromium oxide film with self-repairing ability upon high temperature sliding. The present approach could help to shed light on the development of novel high-performance chromium oxide films with continuous lubricity from room temperature to elevated temperatures of over 1000 °C.

Reciprocating Wear Behavior of Noncoated and Polymer/Composite Coated AISI 316L Steel: Role of Surface Mechanical Attrition Treatment

The current work investigates the reciprocating wear behavior of surface mechanical attrition–treated (SMAT) AISI 316L stainless steel with and without polymer and composite coatings. The high-performance aromatic thermoset polymer (ATSP) and its composite with MoS2 are deposited on non-SMATed and SMATed steel using the spin coating technique. Further, a reciprocating wear test is performed on non-SMATed, SMATed, and coated surfaces against an alumina ball using different loads and reciprocation cycles. Enhanced surface hardness (∼89%), presence of an α′ (body-centered cubic [bcc] Fe) phase, and lower oxidation during reciprocation cause a decrease in wear loss and coefficient of friction (COF) of the SMATed surface by ∼37, and ∼20%, respectively, under 15 N load and most extended reciprocation cycle. The wear loss and COF of the steel are further reduced by depositing ATSP polymer and ATSP-MoS2 composite coatings. The adhesion and durability of coatings are enhanced by the SMAT process. This enhanced durability lowers the wear loss and COF of ATSP and ATSP-MoS2 composite coatings when deposited on the SMATed substrate. Polymer coating reduces the COF of non-SMATed and SMATed steel by ∼68 and ∼85%, respectively. Depending on the concentration of MoS2 in the composite coating, the COF ranges from 0.04 to 0.32 and from 0.02 to 0.07 for non-SMATed and SMATed specimens, respectively. The best performance of a composite coating was observed at ∼10 wt% MoS2. The COF of composite coated steel is ∼96% lower than that of the noncoated and nontreated steel surface. The SMAT processing of substrate and ATSP-MoS2 composite coating considerably enhances the tribological performance of AISI 316L steel.

Study on alumina ball size distribution in white cement grinding

This paper presents the results of the characterization of alumina ball size distribution in the mill of a crushing and grinding plant. The mill was unloaded and the balls were sieved. Then, the results were adjusted to three kinds of models; two of them are the traditional models of Rosin-Rammler and Gates-Gaudin-Schumann. The third model applied was the Swebrec distribution function, which has been successfully used on fragmented rock size distribution. The best adjustment for the ball size distribution was obtained by the Swebrec function, with a correlation coefficient of 0.9984.